Re: [PATCH] tracing: always define trace_{irq,preempt}_{enable_disable}

From: Arnd Bergmann <arnd@arndb.de>
To: Joel Fernandes <joelaf@google.com>
Cc: Steven Rostedt <rostedt@goodmis.org>,
	Ingo Molnar <mingo@redhat.com>,
	LKML <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH] tracing: always define trace_{irq,preempt}_{enable_disable}
Date: Thu, 19 Oct 2017 18:04:03 +0200	[thread overview]
Message-ID: <CAK8P3a1UgCLx4BR01tY7oTNjdBCjL6erK7geCZuE2pHSUcgq3g@mail.gmail.com> (raw)
In-Reply-To: <CAJWu+oqZdsA68Cs0CGF4ixULtWcsEkrhoe7oSTbZDf5wb8TDSw@mail.gmail.com>

On Thu, Oct 19, 2017 at 5:42 PM, Joel Fernandes <joelaf@google.com> wrote:
> Hi Arnd,
>
> On Thu, Oct 19, 2017 at 1:32 AM, Arnd Bergmann <arnd@arndb.de> wrote:
>> We get a build error in the irqsoff tracer in some configurations:
>>
>> kernel/trace/trace_irqsoff.c: In function 'trace_preempt_on':
>> kernel/trace/trace_irqsoff.c:855:2: error: implicit declaration of function 'trace_preempt_enable_rcuidle'; did you mean 'trace_irq_enable_rcuidle'? [-Werror=implicit-function-declaration]
>>   trace_preempt_enable_rcuidle(a0, a1);
>>
>> The problem is that trace_preempt_enable_rcuidle() has different
>> definition based on multiple Kconfig symbols, but not all combinations
>> have a valid definition.
>>
>> This changes the conditions so that we always get exactly one
>> definition of each of the four tracing macros. I have not tried
>> to verify that these definitions are sensible, but now we
>> can build all randconfig combinations again.
>>
>
> Thanks for catching this. I didn't follow why it breaks for you,
> especially I'm troubled by your proposal of defining the empty macro
> for !defined(CONFIG_DEBUG_PREEMPT) in your patch. Could you provide
> your config sample and architecture you're building for? I'm guessing
> its ARM but let me know. I will try to build it and reproduce it.

I ran into it during an arm64 randconfig build, uploaded the config file to
https://pastebin.com/s5AiqXTM

        Arnd

> thanks,
> Joel